Method and system for the secure distribution of compressed digital texts

ABSTRACT

A process for the secure distribution of compressed digital texts formed by blocks of binary data stemming from digital transformations applied to an original text, and including two stages: a preparatory stage including modifying at least one binary data in one of the blocks according to at least one substitution operation including extraction of the binary data in a block and its replacement by a decoy, and a transmission stage of a modified compressed digital text in conformity with the format of the original text, constituted of blocks modified during the course of the preparatory stage, and by a separate path of the modified compressed digital text, of digital complementary information permitting reconstitution of the original compressed digital text on the equipment of the addressee from the modified compressed digital text and from the complementary information.

RELATED APPLICATION

This is a §371 of International Application No. PCT/FR2005/000553, withan international filing date of Mar. 8, 2005 (WO 2005/088902, publishedSep. 22, 2005), which is based on French Patent Application No.04/50463, filed Mar. 8, 2004.

TECHNICAL FIELD

This disclosure relates to the area of binary data from transformationsapplied to digital texts.

BACKGROUND

It is possible with the current solutions to transmit voluminous textsand documents in digital form via telecommunication networks of thecable, DSL (Digital Subscriber Line) or BLR (Local Radio Loop) type.Furthermore, to avoid the pirating of works and confidential documentsbroadcast in this manner, the latter are frequently encrypted orscrambled by various well known means.

As concerns the secure distribution of texts and binary data, WO98/05142 discloses a process and equipment for the protection of dataand their secure transmission through an electronic network. Thedocument concerns the encryption of textual data with the aid ofmatrices of ASCII characters generated by keys. The three key elementsat the input are a PIN code (Personal Identification Number), the numberof the bank account of the user and a password. These three keysinitiate the generation of a matrix A and a matrix B. Matrices A and Bare generated in a pseudorandom manner with the aid of an analyticfunction such as a logarithmic function, a trigonometric function, asquare root function or the like. The distribution of characters inmatrices A and B is irregular and each character is unique. Threeintegrity control values are calculated and incorporated in theprotected stream, one of which represents the sum of the input textualdata and the two others are relative to the three input key elements.The input data is transformed into a decimal value with four numbers byoperations of permutation, addition, subtraction, multiplication,division and they are then divided into two values of two numbers. Thesetwo values are indexed relative to the elements of matrices A and B toform the stream of protected data. However, due to the division into twoparts for the indexation, the size of the protected stream increasesconsiderably relative to the size of the initial data. Moreover, all theprotected data, as well as the three control values generated, arepresent in the protected data. Therefore, WO '142 does not correspond tothe criteria of high security.

SUMMARY

This disclosure relates a process for secure distribution of compresseddigital texts formed by blocks of binary data stemming from digitaltransformations applied to an original text including modifying at leastone binary data in one of the blocks according to at least onesubstitution operation including extracting the binary data in a blockand replacing it with a decoy, transmitting a modified compresseddigital text in conformity with a format of the original compresseddigital text including modified blocks, transmitting by a separate paththe modified compressed digital text and digital complementaryinformation, and reconstituting the original compressed digital text bya calculation on equipment of an addresses as a function of the modifiedcompressed digital text and of the complementary information.

This disclosure also relates a system for implementing the process forsecure distribution of compressed digital texts including at least oneserver containing original compressed digital texts, an apparatus foranalyzing the compressed digital text, an apparatus for separating theoriginal compressed digital text into a modified compressed digital textand into complementary information as a function of the analysis, atleast one telecommunication network for transmitting, and at least oneapparatus in equipment of an addressee for recomposition of the originalcompressed digital text as a function of the modified compressed digitaltext and the complementary information.

BRIEF DESCRIPTION OF THE DRAWING

The disclosure will be better understood with the aid of thedescription, given below purely be way of explanation, of one aspect ofthe system with reference made to attached FIG. 1, that illustrates aparticular aspect of the system permitting the protection anddistribution in a secure manner of compressed digital texts.

DETAILED DESCRIPTION

We supply a system that permits the protection and the distribution in asecure manner of compressed digital texts and the restitution of theoriginal digital text while preventing a non-authorized use of or accessto these compressed digital texts.

The term “text” defines a succession of characters from an alphabet ofletters or numbers and of punctuation signs.

The term “digital text” defines the succession of bytes representingcharacters from an alphabet and/or punctuation signs and/or data forformatting and displaying a text on a viewing screen.

The term “compressed digital text” defines the binary data stream froman algorithm of statistical compression applied to the digital text.

The action of displaying a compressed digital text is defined as theseries of operations including reading and decoding the succession ofbinary data that constitutes the compressed digital text for restitutingthe text on a viewing screen such that it can be read and understoodfrom a semantic viewpoint by a human being.

In particular, we provide an apparatus capable of transmitting in asecure manner a set of compressed digital texts to a viewing screenand/or for being recorded on the hard disk of a computer or on therecording support of a box connecting the telecommunication network to aviewing screen such as a television screen or a personal computermonitor while avoiding any fraudulent use such as the possibility ofmaking illicit copies of textual contents or of compressed digitaltexts. The invention also relates to a client-server system between theserver that furnishes the secure compressed digital texts and the clientthat displays, reads, records or prints the compressed digital texts.

The protection of compressed digital texts is based on the principle ofdeletion and replacement of certain information coding the originalcompressed digital texts by any method, e.g., substitution,modification, permutation or shifting of the information. Thisprotection is also based on a knowledge of the structure of the binarydata at the output of the encoder producing the compressed digitaltexts.

We address the general principle of a process for securing compresseddigital texts. The solution includes extracting and permanentlypreserving, in a location that cannot be accessed by the user, in fact,in the distribution network, a part of the compressed digital textrecorded at the client's or sent online, which part is of primeimportance for exploiting the compressed digital text on a displayscreen, but has a very low volume relative to the total volume of thecompressed digital text recorded at the user's or received online. Thelacking part will be transmitted via the distribution network at themoment of the exploitation of the compressed digital text.

As the compressed digital text is separated into two non-equal parts,the larger part of the compressed digital text is called the “modifiedcompressed digital text” and is therefore transmitted via a classicbroadband or narrowband broadcasting network whereas the lacking partcalled the “complementary information” is sent on demand via anarrowband telecommunication network such as the classic telephonenetworks or cellular networks of the GSM, GPRS, or UMTS type or by usinga small part of a network of the DSL or BLR type, or by using a subsetof the bandwidth shared on a cable network, or also via a physicalsupport such as a memory card or any other support. The two networks canadvantageously be combined while retaining the two separate transmissionpaths. The original compressed digital text is reconstituted on theequipment of the addressee by a synthesis module from the modifiedcompressed digital text and the complementary information.

To implement the process, we provide a protection system comprising ananalysis and protection module and a recomposition module that are basedon a digital format stemming from the encoding of a digital text usingstatistical compression algorithms. The analysis and protection moduleis based on the substitution by “decoys” or on the modification of partof the binary data composing the original compressed digital text. Thefact of having removed and substituted a part of the original data ofthe original compressed digital text during the generation of themodified compressed digital text does not permit the recomposition ofthe original compressed digital text from only the data of the modifiedcompressed digital text.

Based on the characteristics of the compressed digital text, severalvariants of the protection process are implemented and illustrated withselected examples.

We more particularly provide an apparatus capable of transmitting in asecure manner a digital text to a display device and/or for beingrecorded in the memory of the backup apparatus of a box connecting thetelecommunication network to the display device while preserving thesemantic content of the text, but avoiding the possibility that thedigital text could be read and copied illicitly.

A compressed digital text generated by a statistical compressionalgorithm from a digital text is constituted of a succession of binarydata representing codes and or entries in coding tables and/or pointersto the positions in the digital text.

The process includes, after analysis of the compressed digital text,extracting at least one original binary data in the compressed digitaltext, which original binary data represents a code or an entry in acoding table or a pointer, which data is randomly selected, and inreplacing it by a binary data called a decoy of the same size and of thesame nature, but with a random value to generate a compressed digitaltext in conformity with the format of the original compressed digitaltext. The displaying of the modified compressed digital text thenrestores a text that is illegible and/or incomprehensible from asemantic viewpoint for a human being.

The original binary data to be extracted may be selected in adeterministic manner.

The value of the decoy binary data may be calculated in a deterministicmanner.

The decoy binary data may have a size different from the size of theoriginal binary data.

The process thus relates to the secure distribution of compresseddigital texts formed by blocks of binary data stemming from digitaltransformations of applied to an original text, characterized in that itcomprises:

-   -   a preparatory stage including modifying at least one binary data        in one of the blocks according to at least one substitution        operation including extraction of the binary data in a block and        its replacement by a decoy,    -   a transmission stage:        -   i. of a modified compressed digital text in conformity with            the format of the original compressed digital text,            constituted of blocks modified during the course of the            preparatory stage, and        -   ii. by a separate path of the modified compressed digital            text, of digital complementary information permitting            reconstitution of the original compressed digital text from            the calculation on the equipment of the addressee as a            function of the modified compressed digital text and the            complementary information.

The binary data may represent an entry into a coding table and the decoyrepresents a different entry into the coding table.

The coding table may be constructed in a dynamic manner during thedecoding.

The coding table is advantageously predefined by a given standard or agiven norm.

The binary data advantageously represents a prior position in thedigital text generated in the course of the decoding and the decoyrepresents a different prior position in the digital text generated inthe course of the decoding.

The modified compressed digital text 5 may be in conformity with thestandard of the original compressed digital text 1.

The modified compressed digital text 5 may be in conformity with theformat of the original compressed digital text 1.

The binary data and the decoy may have the same size.

The binary data and the decoy may have different sizes.

The series of binary data is preferably coded differentially.

The modified compressed digital text may have the same size as theoriginal compressed digital text.

The modified compressed digital text may have a size different than thatof the original compressed digital text.

The compressed digital text reconstituted from the modified compresseddigital text is preferably strictly identical to the original compresseddigital text.

The process is advantageously applied to compressed digital textsstemming from the LZW compression format.

The process is advantageously applied to compressed digital textsstemming from the ZLIB/DEFLATE compression format.

The process is advantageously applied to compressed digital textsstemming from the Adobe PDF format.

The process is advantageously applied to compressed digital imagesstemming from the TIFF format.

The process is advantageously applied to compressed digital imagesstemming from the GIF format.

We also provide a system for implementing the process, comprising atleast one server containing original compressed digital texts andcomprising an apparatus for analyzing the compressed digital text, anapparatus for separating the original compressed digital text into amodified compressed digital text and into complementary information as afunction of the analysis, at least one telecommunication network for thetransmission and at least one apparatus in the equipment of theaddressee for the recomposition of the original compressed digital textas a function of the modified compressed digital text and thecomplementary information.

The systems and processes will be better understood with the aid of thefollowing examples concerning statistical compression algorithms ofdigital texts well known in the art.

The LZW (Lempel-Ziv-Welch) compression algorithm is a statisticalcompression algorithm that can be adapted to a variable length and thathas been adapted in particular as a compression standard in the TIFF(Tag Image File Format), GIF (Graphics Interchange Format) or Adobe PDF(Portable Document Format) standards. The LZW algorithm also compressesbinary data (byte stream) as well as visual data (pixel stream) or alsothe data of a digital text.

The data stemming from the LZW compression algorithm includes a sequenceof codes that have a length comprised between 9 and 12 bits. Each coderepresents either a simple character (that is, a byte comprised between0 and 255), a table re-initialization marker (value 256), an “end ofdata” marker (value 257) or also an entry into a table (value>258),which entry is associated with a sequence of bytes found previously inthe digital text to be compressed. Initially and in the encoding as wellas in the decoding the codes have a length of 9 bits (value comprisedbetween 0 and 257) and the table is initialized with the 258 firstentries (the 256 values of a byte+the re-initialization marker 256+theend of data marker 257).

As the encoding (or decoding) process progresses, new codes are added tothe table, each associated with sequences of bytes with variable lengthsthat can appear in a recurrent manner in the digital text to becompressed (or decompressed). Each time that a byte sequence that hasalready appeared reappears in the digital text the code corresponding tothe entry of the table storing this same sequence is sent to thecompressed digital text. Likewise, during decompression, the codes aresystematically replaced by the byte sequence read at the correspondingentry of the table and a new entry is added to the table to store thesequence formed from the previously decoded sequence. Thus, the table isconstructed dynamically in the same manner in the encoding as in thedecoding.

When the binary length of the codes is no longer sufficient forrepresenting an entry in the table, it is increased by 1: Thus, as soonas the number of entries in the table reaches 510, the codes are codedon 10 bits (and in the same manner when the entry number reaches 1022(11 bits) and 2046 (12 bits). However, the codes never exceed a lengthof 12 bits (4095 entries maximum). In a compressed digital text the code256 can appear several times: The table is then reinitialized and thebinary length of the codes re-initialized to 9.

During the protection operation of a compressed digital text stemmingfrom the LZW algorithm, an algorithm reads the byte stream anddynamically constructs the table in the same manner as an LZWdecompression algorithm.

The protection operation of an LZW compressed digital text includesextracting in a random and/or deterministic manner in the sequence oneor several (this number is determined in a random or calculated manner)original codes and in replacing them by one or several valid “decoy”codes, which valid “decoy” codes point to entries in the table. A“decoy” code is called valid when the new pointed entry in the tableexists and then the entry corresponds to a sequence of bytes with alength identical to that pointed by the original code.

The digital text decompressed from the modified compressed digital texthas the same size as the original digital text. The text displayed fromthe modified compressed digital text includes a random succession ofalphabetical characters and punctuation signs that is not intelligibleto a human being.

The Adobe PDF (Portable Document Format) format uses the LZW statisticalcompression algorithm for compressing objects of the digital text typein a document encoded in the PDF format. An object of the digital texttype represents a paragraph, one or several pages of text, the legend ofa figure. Each object of the digital text typed is coded in anindependent manner. Thus, the process allows the protection of certaindigital texts to render the displayed text illegible and/orincomprehensible while leaving other texts objects in the same PDFdocument readable and comprehensible.

The process permits the protection of objects of the figure and digitalimage type incorporated in a text document and stemming from astatistical compression algorithm by making them incoherent from theviewpoint of human visual perception while leaving text objects in thesame PDF document readable and comprehensible.

The process advantageously permits the protection of digital images inthe TIFF and GIF formats by making them incoherent from the viewpoint ofhuman visual perception.

The zlib/deflate compression algorithm is a combination of twostatistical compression algorithms: Huffman and LZ77 (Lempel-Ziv 77). Itis used especially for compressing objects of the digital text and/ordigital image and/or figure type in the Adobe PDF format.

The Huffman algorithm includes replacing a succession of symbols in anoriginal stream and stemming from a certain alphabet by a series ofcodes with variable lengths, each code substituting a symbol in thecompressed stream. The algorithm begins by analyzing the number andfrequency of the symbols appearing in the original stream to construct acoding tree from which it associates each encountered symbol with a codewith a length inversely proportional to the frequency of the appearanceof the symbol in the original stream. The compression then replaces eachsymbol with its associated code. However, the decompression algorithmneeds the coding tree to decompress the compressed stream. However, amodified version of Huffman is used for the zlib/deflate algorithm: Thecoding tree is constructed respecting the supplementary rules thatconfer a property of unicity to it and the decompression algorithm nolonger needs the coding tree, but only the lengths of the codes used toreconstruct the latter.

Algorithm LZ77 identifiers the sequences of recurrent data in a streamin a sliding window of fixed size. When a sequence that has alreadyappeared is detected again, it is replaced in the compressed stream bytwo numbers: A distance d and a length l. The distance indicates atwhich location in the window the same sequence begins and the lengthindicates how much data the identified sequence comprises. During thedecompression, each time the algorithm encounters a couple (d, l) itrecopies in the exiting stream the sequence of data with length l readfrom the current position less d.

The zlib/deflate compression algorithm uses three compression modes: A“no compression” mode for the data that has already been compressed, aclassic LZ77+Huffman mode with the coding trees defined in thespecifications of the algorithm, and a modified LZ77+Huffman mode. Thedata is cut into blocks with each block being coded independentlyaccording to one of the three previously cited modes.

In modes 2 and 3 the data is first coded according to LZ77 and asequence of symbols is thus generated, which symbols are of the“character” (i.e., a byte whose value is comprised between 0 and 255)type or distance-length (d, l) couple type. This symbol sequence is thencompressed with a classic Huffman algorithm (mode 2) or a modifiedHuffman (mode 3).

The operation for protecting a compressed digital text according to thezlib/deflate algorithm includes modifying one or several blocks codedaccording to modes 2 or 3. The modifications include extracting from thecompressed digital text a Huffman code coding a symbol of the“character” or distance d type and replacing it with a valid Huffmancode. A Huffman code is called valid if it has the same length as thecode that it replaces and if it corresponds effectively to a codedsymbol of the same type, that is, character or distance.

A modified zlib/deflate compressed digital text has the same size as theoriginal zlib/deflate compressed digital text. Likewise, thedecompressed digital text from the modified compressed digital text hasthe same size as the original digital text.

Displaying the modified digital text produces a text that is illegibleand/or incomprehensible for a human being because it displays asuccession of characters and punctuation signs with no logic.

The specifications of the zlib format define a field of 4 bytes ADLER32located at the end of the compressed digital texts: This field stores aunique identifier of the original digital text and it is used during thedecompression to verify the integrity of the digital text. In the caseof a compressed and modified zlib/deflate digital text, the signature ofthe decompressed digital text will not be identical to that of theoriginal digital text.

The original signature is advantageously updated during the applicationof the protection.

Turning now to FIG. 1, compressed digital text 1 to be secured is passedvia link 2 to analysis and protection module 3 that generates a modifiedcompressed digital text 5 in a format identical to original compresseddigital text 1 except that certain binary data have been replaced byvalues different than the original ones, and is stored in server 6. Thecomplementary information 4 of any format is also placed in server 6 andcontains information relative to the data of the compressed digital textthat was modified, replaced, substituted or shifted, and to its valuesor emplacements in the original compressed digital text.

Protected compressed digital text 5 in a format identical to theoriginal compressed digital text is advantageously then transmitted viaa high throughput network 9 of the microwave, cable, satellite type oranother network to the terminal of the user 8 and more precisely into amemory 10.

When user 8 requests to display text present in memory 10, twopossibilities are possible: Either user 8 does not have all the rightsnecessary to exploit the compressed digital text, in which case themodified compressed digital text 5 generated by protection module 3 andpresent in memory 10 is passed to synthesis system 13 via reading buffermemory 11, that does not modify it and transmits it identically to adisplay device capable of decoding it 14 and its contents, degraded byprotection module 3 and incomprehensible from a semantic viewpoint, andis displayed on viewing screen 15. Modified compressed digital text 5generated by protection module 3 is advantageously passed directly vianetwork 9 to reading buffer memory 11 then to synthesis module 13.

Or, server 6 decides that user 8 has the rights to correctly display thecompressed digital text. In that case, synthesis module 13 makes adisplay request to server 6 containing complementary information 4necessary for the recomposition of the original compressed digital text1. Server 6 then sends complementary information 4 via telecommunicationnetwork 7 of the analog or digital telephone line type, DSL (DigitalSubscriber Line) or BLR (Loop Local Radio) type, via DAB networks(Digital Audio Broadcasting) or via digital mobile telecommunicationnetworks (GSM, GPRS, UMTS) 7, which complementary information permitsthe reconstitution of the compressed digital text in such a manner thatuser 8 can store it in buffer memory 12. Synthesis module 13 thenproceeds to the reconstitution of the original compressed digital textfrom the modified compressed digital text that it reads in its readingbuffer memory 11, and modified fields, whose positions it knows, as wellas the original values are restored by virtue of the content of thecomplementary information read in recomposition buffer memory 12.Complementary information 4 that is sent to the recomposition module isspecific for each user and is a function of his rights, e.g., single ormultiple use, the right to make one or several private copies, late orearly payment.

Modified compressed digital text 5 is passed directly via network 9 toreading buffer memory 11 then to synthesis module 13.

Modified compressed digital text 5 is advantageously recorded on aphysical support like a disk of the CD-ROM or DVD type, a hard disk or aflash memory card. Modified compressed digital text 5 is then read fromphysical support 9 bis by disk reader 10 bis of box 8 in order to betransmitted to reading buffer memory 11, then to recomposition module13.

Complementary information 4 is advantageously recorded on a physicalsupport 7 bis with a credit card format constituted of a smart card or aflash memory card. This card 7 bis is then read by module 12 of theapparatus 8 comprising a card reader 7 ter.

Card 7 bis advantageously contains the applications and the algorithmsthat will be executed by recomposition module 13.

Apparatus 8 is advantageously an autonomous, portable and mobileapparatus.

1. A process for secure distribution of compressed digital texts formedby blocks of binary data stemming from digital transformations appliedto an original text, comprising: configuring at least one processordevice to perform functions of: modifying at least one instance ofbinary data randomly selected in at least one of the blocks according toat least one substitution operation comprising extracting the binarydata to be modified and replacing it with at least one decoy to provideat least one modified block, wherein the binary data to be modified isindicative of a reference to at least a first other instance of thebinary data and the decoy is indicative of a reference to at least asecond other instance of the binary data different than the at least onefirst other instance of the binary data; storing the at least onemodified block in a memory; transmitting a modified compressed digitaltext in conformity with a format of the original compressed digitaltext, the modified compressed digital text comprising the stored atleast one modified block; and transmitting, by a separate path from thetransmission of the modified compressed digital text, digitalcomplementary information; wherein, the transmitting enables theoriginal compressed digital text to be reconstituted by a calculation onequipment of an addressee as a function of the modified compresseddigital text and the complementary information.
 2. The process accordingto claim 1, wherein the modifying at least one instance of the binarydata comprises modifying data indicative of an entry into a coding tablewith data indicative of a different entry into the coding table.
 3. Theprocess according to claim 1, wherein modifying at least one instance ofthe binary data includes modifying binary data with a decoy that has thesame size.
 4. The process according to claim 1, wherein modifying atleast one instance of the binary data includes modifying binary datawith a decoy that have different sizes.
 5. The process according toclaim 1, further comprising coding the binary data differentially. 6.The process according to claim 1, wherein transmitting a modifiedcompressed digital text includes transmitting a modified compresseddigital text that is in conformity with a standard applicable to theoriginal compressed digital text.
 7. The process according to claim 1,wherein transmitting a modified compressed digital text includestransmitting a modified compressed digital text that is in conformitywith a format applicable to the original compressed digital text.
 8. Theprocess according to claim 1, wherein transmitting a modified compresseddigital text includes transmitting a modified compressed digital textthat has the same size as the original compressed digital text.
 9. Theprocess according to claim 1, wherein transmitting a modified compresseddigital text includes transmitting a modified compressed digital textthat has a size different from the original compressed digital text. 10.The process according to claim 1, applied to compressed digital textsstemming from an Lempel-Ziv-Welch compression format.
 11. The processaccording to claim 1, applied to compressed digital texts stemming froma ZLIB/DEFLATE compression format.
 12. The process according to claim 1,applied to compressed digital texts stemming from a Portable DocumentFormat format.
 13. The process according to claim 1, applied tocompressed digital images stemming from a Tagged Image File Formatformat.
 14. The process according to claim 1, applied to compresseddigital images stemming from a Graphics Interchange Format format.
 15. Aprocess for secure distribution of compressed digital texts formed byblocks of binary data stemming from digital transformations applied tooriginal texts, comprising: configuring at least one processor device toperform the functions of: receiving, by separate paths, a modifiedcompressed digital text and a digital complimentary informationrespectively: the modified compressed digital text having at least atleast one instance of binary data randomly selected in at least one ofthe blocks replaced with at least one decoy, the binary data that wasreplaced being indicative of a reference to at least a first otherinstance of the binary data and the decoy being indicative of areference to at least a second other instance of the binary datadifferent than the at least one first other instance of the binary data,and the digital complementary information; and reconstituting anoriginal compressed digital text by a calculation on equipment of anaddressee as a function of the modified compressed digital text and thecomplementary information.
 16. The process according to claim 15,further comprising constructing the coding table in a dynamic mannerduring reconstituting.
 17. The process according to claim 16, whereinconstructing the coding table includes constructing a coding table thatis predefined by a given standard or a given norm.
 18. The processaccording to claim 15, wherein the reconstituting includes modifying thedecoy that represents a prior position in the digital text with binarydata that represents a different prior position in the digital text. 19.The process according to claim 15, wherein compressed digital textreconstituted from the modified compressed digital text is identical tothe original compressed digital text.
 20. A system for securelydistributing an original compressed digital media comprising blocks ofdata stemming from digital transformations applied to at least oneoriginal work, the system comprising: means for replacing at least oneinstance of the data in at least one of the blocks with at least onesubstitute to provide at least one modified block, wherein the data tobe replaced is indicative of a reference to at least a first otherinstance of the data in at least one of the blocks and the substitute isindicative of a reference to at least a second other instance of thedata in at least one of the blocks different than the at least one firstone other instance of the data; means for transmitting a modifiedcompressed digital media, the modified compressed digital media being inconformity with a format of the original compressed digital media andcomprising the at least one modified block; and means for transmitting,by a separate path from the modified compressed digital media,complementary information, wherein the complementary information issuitable for use with the modified compressed digital media to reproducethe original compressed digital media.
 21. The system according to claim20, wherein the means for replacing at least one instance of the datacomprises means for replacing data indicative of an entry into a codingtable with data indicative of a different entry into the coding table.22. The system according to claim 20, wherein the means for replacing atleast one instance of the data includes means for replacing data with adecoy that has the same size.
 23. The system according to claim 20,wherein the means for replacing at least one instance of the dataincludes means for replacing data with a decoy that have differentsizes.
 24. The system according to claim 20, further comprising meansfor coding the data differentially.
 25. The system according to claim20, wherein the means for transmitting a modified compressed digitaltext includes means for transmitting a modified compressed digital textthat is in conformity with a standard applicable to the originalcompressed digital text.
 26. The system according to claim 20, whereinthe means for transmitting a modified compressed digital text includesmeans for transmitting a modified compressed digital text that is inconformity with a format applicable to the original compressed digitaltext.
 27. The system according to claim 20, wherein the means fortransmitting a modified compressed digital text includes means fortransmitting a modified compressed digital text that has the same sizeas the original compressed digital text.
 28. The system according toclaim 20, wherein the means for transmitting a modified compresseddigital text includes means for transmitting a modified compresseddigital text that has a size different from the original compresseddigital text.
 29. A non-transitory computer-readable storage mediumhaving instructions stored thereon, which in response to execution by aprocessor, results in a machine performing the operations of: replacingat least one instance of the data in at least one of the blocks with atleast one substitute to provide at least one modified block, wherein thedata to be replaced is indicative of a reference to at least a firstother instance of the data in at least one of the blocks and thesubstitute is indicative of a reference to at least a second otherinstance of the data in at least one of the blocks different than the atleast one first one other instance of the data; transmitting a modifiedcompressed digital media, the modified compressed digital media being inconformity with a format of the original compressed digital media andcomprising the at least one modified block; and transmitting, by aseparate path from the modified compressed digital media, complementaryinformation, wherein the complementary information is suitable for usewith the modified compressed digital media to reproduce the originalcompressed digital media.
 30. The computer-readable medium of claim 29,wherein the instructions for replacing at least one instance of the datacomprise instructions for replacing data indicative of an entry into acoding table with data indicative of a different entry into the codingtable.
 31. The computer-readable medium of claim 29, wherein theinstructions for replacing at least one instance of the data includeinstructions for replacing data with a decoy that has the same size. 32.The computer-readable medium of claim 29, wherein the instructions forreplacing at least one instance of the binary data include instructionsfor replacing binary data with a decoy that have different sizes. 33.The computer-readable medium of claim 29, further comprisinginstructions for coding the data differentially.
 34. Thecomputer-readable medium of claim 29, wherein the instructions fortransmitting a modified compressed digital text include instructions fortransmitting a modified compressed digital text that is in conformitywith a standard applicable to the original compressed digital text. 35.The computer-readable medium of claim 29, wherein the instructions fortransmitting a modified compressed digital text include instructions fortransmitting a modified compressed digital text that is in conformitywith a format applicable to the original compressed digital text. 36.The computer-readable medium of claim 29, wherein the instructions fortransmitting a modified compressed digital text include instructions fortransmitting a modified compressed digital text that has the same sizeas the original compressed digital text.
 37. The computer-readablemedium of claim 29, wherein the instructions for transmitting a modifiedcompressed digital text include instructions for transmitting a modifiedcompressed digital text that has a size different from the originalcompressed digital text.